Tolkien adapted the Nordic dwarf--a short, stout, human inhabitant of mountain and underground regions often possessing great metallurgy skills (Wikipedia)--and left them mostly unaltered from their basic mythological origin. In Gimli, Tolkien developed the dwarf as a caricature of stubbornness and strength, which would be translated in Dungeons and Dragons as a fighter-class race. Gimli's persona would be replicated in other RPGs using dwarves, particularly in the Final Fantasy series, while their renown as engineers and smiths would be more widespread.

According to Wikipedia, the immortal Elves dwell in forests, caves, near springs and in wells. The youthful-looking demi-gods have been a staple creature within several European mythologies, although they are of Germanic origin. In Lord of the Rings, they have been transformed into a "fair race" similar to humans, also bearing a sophisticated oral and written language (Appendix F, 1101-2). Legolas, an elf who has accompanied Frodo in the Fellowship of the Ring, was an expert archer. The linkage between elves and archery made through Legolas's character was passed down to Dungeons and Dragon in the enhanced archery skills granted to elves, while their intelligence was translated to magical expertise in other RPGs.

Unlike the elf, orcs--as a humanoid, subterranean race manipulated by Sauron for war--was primarily a Tolkien creation, although the term "orc" is Latin for "demon," and some epics from the medieval era depicts orcs as a maritime monster. Also known as "goblins," the orcs in other RPGs often borrow the short temper and repugnant appearance portrayed in Lord of the Rings.

Trolls in Scandinavian mythology were mischievous humanoids characterized with large noses, varying height, and minimal intellect (Wikipedia). In Lord of the Rings, they are over 9 feet tall and are violent servants of Sauron, and sometimes are viewed as oversized orcs (Lord of the Rings, Appendix F, 1105-6). While trolls in RPGs have diversified considerably in both appearances and allegiances, Lord of the Rings helped popularize trolls in the US and Canada, and in effect encouraged their use in Dungeons and Dragons. Trolls in RPGs developed since Dungeons and Dragons, however, do not resemble those in Lord of the Rings as strongly as dwarves, elves and other races and elements derived from the novel, and that could be attributed to the established yet unpronounced nature of this character in folklore.

In literature, anyone with the power to control their environment in a supernatural manner could become a wizard, and in fact, "they are wizards precisely because of their control of fantastic powers beyond our conception of reality" (Victorian Web).Of the mortal races, elves and humans were the only two in Lord of the Rings who possessed any noticeable magical ability, although the five wizards--Gandalf and Saruman among them--were supernatural beings rather than human, as Gandalf's rebirth after fighting the Balrog makes evident. Despite this, the wizards still have desires, ambitions, and concerns that are distinctly human in nature. The great power yet human nature of Gandalf and Saruman would be attached to wizards in RPGs, although the swordsmanship Gandalf displayed may have been ignored for the sense of "balance" in relation to character strength.